The present invention relates to a high speed photographic combination for radiographic use and radiography by use thereof, and in particular to a photographic combination for radiographic use, exhibiting high sensitivity and superior image quality, suitable for high quality mammography, and radiography by the use thereof.
For diagnosis of breast cancer, specifically diagnosis of breast cancer at the initial stage, for example, is useful a photographic combination for mammographic use which is comprised of a radiographic intensifying screen and a silver halide photographic material (hereinafter, also referred to as a screen film system), whereby micro-calcification having a size of some hundreds micrometers or less can be detected at the initial stage of cancer. Specifically, relatively low speed photographic materials exhibiting superior graininess are employed in the conventional photographic combination for mammographic use.
To enhance the detectability thereof, further enhanced sharpness in the screen film system has been desired. For example, a radiographic combination of a silver halide photographic material having a silver halide emulsion layer coated on only one side of a support (a so-called single-sided coated film) and a fluorescent screen (or X-ray intensifying screen) in the back screen arrangement is employed to achieve enhanced sharpness. Further, increasing the contrast of the single-sided coated film or prolonging the developing time in processing is conducted to achieve a contrast-increase in the film.
Although sharpness can be enhanced by a contrast-increase of the film, however, there occurs a self-inconsistency such that the contrast-increase results in deteriorated graininess. For example, not only observation of micro-calcification but also detection of a low contrast image of a tumor having a size of about 1 cm is dispensable in diagnosis of breast cancer. Accordingly, enhancement of sharpness without causing deterioration in graininess is desired in mammography.
Deterioration of graininess caused by a contrast-increase of the film can be improved by increasing the X-ray dose, which must be limited in terms of patient exposure to radiation. Further, an x ray source of molybdenum is often employed for mammography since the use of an X ray source giving high exposure to radiation is not suited. Furthermore, there have been made attempts of enhancing graininess of a silver halide photographic material but the size of silver halide grains used in the silver halide photographic material used for mammography is so small that this technique is close to its limitation.
To enhance detectability, micro-calcification images can be can be detected to further smaller levels by applying magnification radiography. This technique is employed in mammography. However, magnification radiography results in blurring of images due to geometrical unsharpness in the detection of tumor. This blurring is unsharpness due to so-called penumbra, depending on the focus size of X ray tube (3) and the magnification factor, shown as blur 5 in FIG. 1. In the mammography used in the field of the medical diagnosis, it was difficult to enhance detectability of both micro-calcification and tumor, with maintaining the patient exposure to radiation at a low level.
It was found by the inventors that this blurring can be overcome by applying a refraction or phase contrast imaging technique. In cases when this technique is allied to mammography, the distance of from X ray tube 3 to photographic combination 2 needs to be increased. In such a case, the use of a high speed photographic combination was found to be effective to overcome the foregoing problems. The combination of the high speed photographic combination with the refraction contrast imaging technique enhances the boundary (or edge) image of the object to be detected, leading to prevention of blurring. In this case, a sharp boundary image was obtained by the use of the high speed photographic combination, without increasing the X-ray dose to the photographic combination. It was further proved that the high speed photographic combination was effective for an enlarged image of fine mineral that was projected onto the photographic combination, even when the intensity of a X ray source was low. Thus, it was found that the use of the high speed photographic combination in the refraction contrast photographing enhances detectability of fine mineral images as well as detectability of tumor, while maintaining the low exposure exposure to radiation.
In view of the foregoing, it is an object of the present invention to provide a photographic combination for radiographic use, exhibiting high sensitivity and superior image quality, suitable for high quality mammography, and radiography by the use thereof.
The above object of the invention can be accomplished by the following constitution:
1. A radiographing system comprising a X ray source and a photographic combination onto which an image of X rays emitted from the X ray source and passing through an object is projected and which comprises a radiographic intensifying screen and a silver halide light sensitive photographic material comprising a support having on only one side of the support a light sensitive layer, wherein the X ray image is one which has been edge-enhanced through refraction contrast enhancement and enlarged, the photographic combination exhibiting a speed of 200 to 750;
2. The radiographic system described above 1, wherein the radiographic system is a mammographic system.
3. The radiographic system described in above 2, wherein the object is a breast;
4. The radiographic system described above 2, wherein the X ray source is a molybdenum tube;
5. The radiographic system described in bove 1, wherein a distance between the X ray source and the object is not less than 50 cm, a distance between the X ray source and the photographic combination being not less than 75 cm;
6. The radiographic system described in above 5, wherein the X ray source is a molybdenum tube;
7. The radiographic system described in above 1, wherein the radiographic intensifying screen exhibits a sensitivity of 200 to 500;
8. The radiographic system described in above 1, wherein the speed of the photographic combination is a system speed based on a photographic speed of the light sensitive layer and a sensitivity of the radiographic intensifying screen;
9. A photographic combination for use in radiography to project a refraction contrast image comprising a radiographic intensifying screen and a silver halide light sensitive photographic material, wherein the photographic material comprises a support having on only one side of the support a light sensitive layer, the photographic combination exhibiting a speed of 200 to 750;
10. The photographic combination of claim 9, wherein the photographic combination is used for mammography;
11. The photographic combination described in above 9, wherein the screen exhibits a sensitivity of 200 to 500;
12. The photographic combination described in above 11, wherein the radiographic intensifying screen exhibits a contrast transfer function of 0.5 to 1.0 at a spatial frequency of 2 line/mm;
13. The photographic combination described in above 9, wherein the radiographic intensifying screen comprises a binder containing a hydrophilic group;
14. The photographic combination described in bove 9, wherein the photographic material exhibits a sensitivity of 1.0 to 3.0 and an average contrast of 2.5 to 4.5;
15. A radiographing method, wherein an refraction contrast radiographic image is photographed using a photographic combination as claimed in claim 9 and wherein an X ray source, an object and the photographic combination are arranged in this order so that the distance between the X ray source and the object is not less than 50 cm and the distance between the object and the photographic combination is not more than 75 cm; and
16. The radiographic method described in above 15, wherein the X ray source is a molybdenum tube.